This invention relates to a key code data generator capable of detecting switches in operation among a number of key switches and function switches and generating key code data for an automatic bass chord performance on the basis of signals from the detected switches.
The specification of U.S. Pat. No. 4,148,017 to the same assignee discloses a key code data generator which detects an on (or off) state of a key switch among a large number of key switches provided on a keyboard of an electronic musical instrument and generates key code data representative of a depressed key in accordance with a result of detection. The specification of U.S. patent application No. 825,443 to the same assignee also discloses a key code data generator which generates key code data to be utilized for an automatic bass performance and an automatic chord performance from key code data representing a depressed key.
Simplification of circuitry and reduction of the number of pins which constitute input and output terminals are major problems to be solved in designing a key code data generator in an integrated circuit configuration.
In the prior art key code data generator disclosed in the U.S. Pat. No. 4,148,017 the key switches are divided into blocks and also grouped by each note name in the respective blocks, and are arranged in a matrix fashion, respective blocks are scanned by a block detection circuit and respective note name groups are scanned by a note detection circuit for detection of a key switch in operation. This arrangement has considerably reduced the number of required input and output lines. The electronic musical instrument employing this prior art key code data generator, however, still requires many signal lines for transmitting signals from a number of function switches if the electronic musical instrument has various performance functions such as the automatic bass/chord performance and the automatic arpeggio performance. Accordingly, this prior art generator is not sufficient for the instrument in respect of the number of signal lines.
The electronic musical instrument proposed in U.S. patent application No. 825,443 detects an on or off state of key switches and function switches, generates key codes representing key switches which are on and generates key code data for the automatic bass chord performance by utilizing signals obtained by decoding these key codes. The construction of this circuit is fairly complicated and it will be difficult to design this circuit in an integrated circuit configuration using only one chip.